Introduction to Thoracic Radiology

Dr. LeeAnn Pack

Dipl. ACVR

Indications

• Coughing• Dyspnea/ Tachypnea• Heart Murmur, Collapse• Primary or Secondary Neoplasia

– Check for metastasis

• Thoracic Trauma• Chest Wall Mass• Exercise Intolerance, Weight Loss

Technical Factors

• Potential for Movement– Decrease mAs

• High inherent contrast area– High kVp

• Collimation• Centering – caudal

scapula– Thoracic inlet to

diaphragm– Pull forelimbs forward

Determining the Phase of Respiration

• Always expose at peak inspiration– Maximizes lung contrast– Inspiratory lateral view

• Caudodorsal aspect of lung caudal to T12• Increased aeration of accessory lung lobe• Separation of heart silhouette and diaphragm

– Inspiratory VD/DV view• Diaphragmatic cupola caudal to mid T8• Lung tips caudal to T10

Inspiratory vs. Expiratory Lateral

Note the space inside the triangle

Inspiratory vs. Expiratory VD

Easy to see the difference in well visualized lung

DV vs. VD

• DV– Less stressful, better for heart– Diaphragm rounded– Caudal pulmonary vessels better visualized– Better to see small amount of pleural air

• VD – Better for lungs– Hear appears elongated– Flat diaphragm – Mickey Mouse ears– Better to see small amount of pleural fluid

DV vs. VD

Right vs. Left Lateral etal.

• Right Lateral– Better cardiac detail– R crus forward– See Cava go into it

• Left Lateral– Heart appears round– L crus forward– See Cava go past

• Anesthesia• Breed Differences

The Effects of Lateral Recumbency

• Lung lesions (mass, nodule, infiltrate) may only be seen on 1 view!!!

• Only the non-dependent (up) lung can be critically evaluated– Dependent lung loses aeration

(atelectasis)• Increases in opacity• Silhouettes with lesions

Interpretation of Thoracic Radiographs

• Heart

• Lungs

• Mediastinum

• Pleural space

• Chest wall

• Bones, Abdomen,Neck

Normal Cardiac Silhouette• Subjective

– Dog = 2 ½ - 3 ½ intercostal spaces– Cat = 2 – 2 ½ intercostal spaces

• 65% or less on VD/DV view

• Objective– Buchanan method

Clock Face

• 11-1 Aortic Arch

• 1-2 Main Pulmonary Trunk

• 2-3 Left Auricle

• 2-5 Left Ventricle

• 5-9 Right Ventricle

• 9-11 Right Atrium

• Centrally – Left Atrium

Lateral View

• Make a Plus sign

• Bermuda triangle

• Left atrium

• Left Ventricle

• Right Ventricle

Thoracic and Pulmonary Vessels

• Aorta• Caudal Vena Cava• Cranial pulmonary

vessels– Proximal third rib

• Caudal pulmonary vessels– 9th rib where crosses

• Veins are ventral and central

Trachea, Bronchial Tree

• Carina – then splits to the main stem bronchi then lobar bronchi

• Tracheal rings can mineralize

• Decreased tracheal diameter– Tracheal narrowing (stenosis, extramural

compression), Tracheal hypoplasia, Tracheal collapse

Lungs

• Normal anatomy– Left

• Cranial (cranial subsegment)

• Cranial (caudal subsegment)

• Caudal

– Right• Cranial

• Middle

• Caudal

• Accessory

The Mediastinum

• Cranial, middle, caudal compartments

• Routinely visible structures:– Heart, trachea, cvc, aorta, +/- thymus, +/-

esophagus– Cranioventral mediastinal reflection– Caudoventral mediastinal reflection

• Aka phrenopericardiac ligament

Mediastinal reflections

Extrathoracic Structures

• Sternum• Vertebrae• Ribs• Adjacent soft

tissues• Diaphragm

The Diaphragm• Cupola

– Cranioventral convex portion

• Right and left crura– Attach to cranioventral

border of L3 and body of L4

– May cause irregularity on these surfaces

• Appearance depends on centering of X-ray beam

The Diaphragm